Low energy consumption thermochromic smart windows with flexibly regulated photothermal gain and radiation cooling

Although the utilization of solar photothermal gain (SPG) (0.28μm–2.5 μm) or infrared radiation cooling (IRC) (2.5 μm–25 μm) enables the thermochromic smart window to play a role in decreasing building energy consumption, the fragmented current research on these properties unfortunately leads to a low efficacy. Herein, based on the simulation of SPG and IRC properties on building energy consumption, a tailored hydrogel is employed in a reversible glass mold with anisotropic infrared radiation emission (ε) in the different surfaces, successfully integrating excellent SPG parameters (phase transition temperature (τC), 28°C, post-phase solar transmittance (Tsol−HT), 3.52%) and IRC parameters (switchable infrared emissivity (Δε), 0.75–0.90). By utilizing summer and winter climate data from Wenzhou, as well as annual climate data from Singapore and Helsinki, it is determined that this gel window may save up to 64.68 MJ/m2, 11.31 MJ/m2, 201.84 MJ/m2, and 60.16 MJ/m2 in the respective locations, when compared to regular glass using the same model in EnergyPlus software. With the exceptional pre-phase visible light transmittance (Tlum−LT=84.86%) and building energy saving performance, the all-day and all-region smart window deserves attention, further investigation, and discourse for alleviating the energy crisis and mitigating greenhouse emissions.